1. Technical Field
The present invention relates to an air conditioning system and an air conditioning method including the steps of: passing a required flow of air intended to be cooled and dehumidified as a main stream through cooling dehumidifying means to cool and dehumidify the air; passing the air through heating means to regulate the air to a predetermined temperature; passing the air through humidifying means to regulate the air to a predetermined humidity; and then merging the air with the reminder of the process air as a side stream so that the air is regulated to a predetermined amount of supply air to be supplied to a use point where industrial activity is carried out.
2. Related Art
The air conditioning systems having the functions of cooling and dehumidifying cools the process air taken in from the outdoors and/or the indoors to its dew point or lower during the passage of the process air through a cooling dehumidifier so that moisture in the process air is condensed to be separated as condensed water. Then, the process air is heated to a predetermined temperature with accuracy and humidified to a predetermined humidity with accuracy to result in the heating-regulated and humidity-regulated air to be supplied to a cleanroom, a clean booth or a clean chamber. Such systems are widely used in manufacturing industries such as semiconductors, various electronic components and various precision components, food industries, pharmaceutical industries, printing industries and the like.
In typical methods of conditioning air which are adopted for cleanrooms, air taken in from the outside of the system is cleaned of fine particles such as dust, mist and the like, and also the temperature and humidity of the air are regulated. Then, the air is uninterruptedly supplied into the cleanroom as supply air, and also the same amount of indoor air as the amount of the supply air is discharged to the outside of the system.
However, the air discharged to the outside of the system is of a temperature and a humidity which have been regulated by use of energy. From the viewpoint of recent energy conservation needs, the structure is modified to be capable of reducing the amount of discharged air as low as possible and regulating the temperature and the humidity of the air expelled from the clean room to allow the recycled use of the air.
In particular, the recent social situation more strongly requires energy conservation. Because of this, in the case of using a refrigerant evaporator in a refrigeration cycle to provide cooling and dehumidification in the related art, as illustrated in FIG. 2, the refrigeration cycle is made up of a compressor 14, an oil separator 16, a condenser 17, an electronic expansion valve 18, cooling dehumidifying means 1, an accumulator 20 and the like that are interconnected by pipes to circulate the refrigerant. Further, air is taken in through an air inlet port 30a of an introducing duct 30, and then is divided into a main-stream duct 37 and a side-stream duct 38. This process air is divided around the ratio of 1 to 1 to flow downstream respectively in the main-stream duct and the side-stream duct in order to reduce the consumption of the cooling and dehumidification energy in the cooling dehumidifying means 1. A process-air flow velocity sensor 34, a process-air temperature sensor 35 and a process-air relative humidity sensor 36 are provided in the introducing duct 30 to measure the flow velocity, the temperature and the relative humidity of the process air taken in, and inputs the measurements to arithmetic means 26.
The cooling dehumidifying means 1 is accommodated in the main-stream duct 37, while flow-rate regulating means 50 is placed in the side-stream duct 38. The flow-rate regulating means 50 is equipped with a flow-rate regulating means actuator 51 for adjustment to the degree of opening of the side-stream duct to maintain constant flow ratio between the main stream and the side stream of the process air flowing downstream in the respective ducts. A side-stream flow velocity sensor 40 is placed in the side-stream duct 38 to measure the flow velocity of the process air flowing in the side-stream duct 38. The measurement is sent to the arithmetic means 26. The main-stream duct 37 and the side-stream duct 38 merge together at the downstream of the cooling dehumidifying means 1 to form a merging duct 39 into which the process air flows.
Heating means 2, humidifying means 3 and a supply-air fan 11 are placed downstream of the confluence. In the air conditioning system shown in FIG. 2, approximately one-half of the overall process air flows into the main-stream duct 37 from the direction of the left arrow, and then is cooled and dehumidified in the cooling dehumidifying means 1. That is, the process air flowing through the main-stream duct 37 is cooled to its dew point or lower during the passage through the cooling dehumidifying means 1, so that the water is separated as condensed water and then discharged to the outside of the air conditioning system. The process air is dehumidified and the temperature of the process air flowing out from the cooling dehumidifying means 1 is measured at a dehumidified air temperature sensor 23.
The air flowing into the cooling dehumidifying means 1 is heat-exchanged with the refrigerant circulating in the refrigeration cycle, so that the air transfers its heat of evaporation to the refrigerant via a heat exchanger tube to be cooled to its dew point or lower. Because the process air taken in is cooled and dehumidified in this manner, passing the process air through the heating means 2 and the humidifying means 3 allows the process air to be regulated to a predetermined temperature and a predetermined humidity. Thus, the process air results in a supply air available in use point. The temperature of the air after the passage through the heating means 2 is measured by a heated air temperature sensor 24.
For a change in the amount of heat required for cooling and the amount of heat required for dehumidification in the cooling dehumidifying means 1, that is, the amount of heat load produced by cooling and dehumidification, an inverter 32 connected to a motor 15 driving the compressor 14 is controlled to change the rpm of the motor 15 to effect a change in the amount of refrigerant circulating in the refrigeration cycle. Also, the power energy of the compressor 14 can be saved.
For a change in temperature of condensation cooling in the cooling dehumidifying means 1, a first temperature sensor 21a and a second temperature sensor 21b are used to detect the refrigerant inlet temperature and the refrigerant outlet temperature in the cooling dehumidifying means 1. In order to change the detected temperature to a set temperature, an electronic expansion valve controller 19 applies a control signal to an electronic expansion valve 18 to regulate the degree of valve opening so that the steam pressure of the refrigerant, that is, the evaporation temperature of the refrigerant is changed.
For regulation of temperature and humidity of the supply air, a supply-air temperature sensor 8 placed around a merging duct outlet 39b in the merging duct 39 detects the temperature and a supply-air humidity sensor 6 detects the humidity. The sensors 8 and 6 input respectively the results to a heating means controller 9 and a humidifying means controller 7, so that the temperature is controlled by the amount of electric power passed through a temperature-rise heater 4 and a humidifying heater 5 which are provided respectively in the heating means 2 and the humidifying means 3. The temperature of humidifier water of the humidifying means 3 is measured by a humidifier temperature sensor 25, and a fluid level of the humidifier water is maintained by a humidifier-water control valve 27. Regarding airflow regulation, an inverter 31 connected to a motor 12 driving a supply-air fan 11 is controlled to achieve energy conservation. In addition, an atmospheric pressure sensor 33 is provided on the exterior surface of the air conditioning system to measure the atmospheric pressure at the location where the system is installed. Then, the measurement is applied to the arithmetic means 26 to be used to regulate the airflow when rapid and great variations in weather conditions occur. Such an air conditioning system is described in, for example, JP-A No. 2004-28421.
A first disadvantageous problem of such an air conditioning method using energy-saving type cooling and dehumidifying functions in the related art is to adopt a vapor-pressure control method in which humidity regulation is expressed in simple relative humidity φ(%). The φ(%) is the percentage of a vapor pressure p(Pa) at this moment with respect to a saturated vapor pressure Ps(Pa) at a temperature t(° C.). For this reason, regulation of the process air to a relative humidity φ(%) can be performed simply by controlling the temperature of humidifier water when humidification is performed to provide a vapor pressure p(Pa), in which controlling the amount of process air and the amount of humidifier water is unnecessary. In other words, a disadvantageous problem that the amount of energy required for necessary humidification is not controlled is caused. When the operation of cooling and dehumidifying the process air is performed through control using a relative humidity φ(%), that is, a vapor pressure, only controlling the cooling dehumidifying temperature is required, and control of the flow rate of the process air is unnecessary. In other words, there is a disadvantageous problem that the amount of energy required for cooling and dehumidification is not controlled. In this manner, the vapor-pressure control method is incapable of controlling the amount of necessary energy, thus constituting an obstacle to the progression of energy conservation technology.
In addition, instead of the passage of the total amount of process air through the cooling dehumidifying means, an amount of air introduced into the main-stream duct as shown in FIG. 2 is determined, as a guide, as 50% or less of the amount of process air. Because of this, in the bypass method in which the amount of air flowing into the main-stream duct is reduced to pass through the cooling dehumidifying means located in the main-stream duct for the purpose of providing energy savings, the flow ratio between the main stream and the side stream is maintained constant in order to select conditions for obtaining condensed water with reliability, in anticipation of a wide range of variations in relative humidity of the process air. Also, flow-rate control for the process air is unnecessary in the vapor-pressure control method for the humidity regulation. Therefore, a disadvantageous problem arises that energy is consumed in cooling and dehumidifying a larger amount of air than necessary.
In addition, since the cooling dehumidifying means is an evaporator in a normal refrigeration cycle, a large refrigerator is required. This gives rise to a disadvantageous problem of requiring high cost for the air conditioning system needing a large space and a large footprint.
As a result of consuming energy in cooling and dehumidifying a larger amount of air than necessary, this gives rise to a disadvantageous problem that a large amount of energy must be inevitably consumed in heating and humidifying.
Further, because the confluence is located upstream of the heating means 2 as shown in FIG. 2, the heating means 2 and the humidifying means 3 handles the combined amount of air. This gives rise to a disadvantageous problem of requiring high cost for the air conditioning system including the heating means 2 and the humidifying means 3 that need a large space and a large footprint. In particular, when the humidifying means 3 is of a basin type in which water is vaporized from a horizontal plane, a wide horizontal plane is required, leading to an increased footprint, resulting in impossibility of providing a compact system.
Next, the following table 1 shows the state of a change in the absolute humidity X(kg/kg (dry air)) under    (A) a high atmospheric pressure of 1033.5 hPa    (B) a standard atmospheric pressure of 1013.3 hPa at sea level    (C) a low atmospheric pressure of 960.5 hPa,when the temperature is adjusted to 25° C. and the relative humidity is adjusted to 50%.
TABLE 1ABCAtmospheric Pressure1033.51013.3960.5(hPa)Absolute Humidity 96.66 × 10−4 98.82 × 10−4104.34 × 10−4X(kg/kg (dry air))
Although the relative humidity φ(%) is not changed, the absolute humidity X decreases under high atmospheric pressure, but the absolute humidity X increases under low atmospheric pressure. It should be understood that, even if the air conditioning system is installed either in the indoors or in the outdoors or is installed either inside a cleanroom or outside a cleanroom, a change in atmospheric pressure affects the process air and the supply air.
The absolute humidity X in Table 1 shows a water content kg included in dry air of 1 kg having no water content under each of the weather conditions. Because of this, disadvantageously, if moisture is regulated by the vapor-pressure control method under a low atmospheric pressure of 960.6 hPa, for example, when a typhoon passes, the humidifier water of (104.34−98.82)×10−4=5.52×10−4 kg greater than that under standard atmospheric pressure is required with respect to dry air of 1 kg, while energy of {(104.34−98.82)×10−4} (51.33×103)=28.33 Joul greater than that under standard atmospheric pressure is required.
Many of the production facilities in which such an air conditioning system is installed are located at 50 m to 1000 m of altitude above seal level, so that the atmospheric pressure in the location has a standard value or lower at all times. Because of this, if the vapor-pressure control method is used for water regulations, this gives rise to a disadvantageous problem of the need for a larger amount of humidifier water and a larger amount of humidification energy than it is installed in a location at sea level at all times.